1. Field of the Invention
The present invention relates to a producing method of a compact, and more particularly, to a producing method of a compact which is formed by being pressed by a punch, the producing method being capable of efficiently and reliably obtaining the compact having a projection which has a sufficient height with respect to its opening width and which has a large tip end side area.
2. Description of Related Art
As a fuel-cell separator, there is conventionally known a gas flow passage on which a plurality of minute projections are provided and through which gas such as hydrogen and oxygen is made to flow. As a producing method of the fuel-cell separator, there is generally known a method of pressing a metal plate by a die and a punch to form a plurality of projections (see Japanese Patent Application Laid-Open No. 2000-317531, for example). It is disclosed in this patent document that a plate 105 is formed into an overhang 120 by a first press die 106 as shown in FIG. 12A and then, a second press die 107 presses an inner side of a peripheral edge of the overhang 120 to form a projection 103 as shown in FIGS. 12B and 12C. According to this, material effectively moves at a projection-forming portion, and this prevents a crack which may be caused due to reduction in plate thickness.
According to the technique of the patent document, however, in order to form the projection 103, it is necessary to carry out two press working operations using at least two press dies 106 and 107, which is nonproductive.
Here, in the case of the fuel-cell separator, if a height of the projection is sufficiently increased with respect to its opening width, a gas flow passage can be made large, and if a tip end side area of the projection is increased, power collection efficiency can be enhanced. According to the technique of the patent document, however, since any of the press working operations using the press dies 106 and 107 is stretch forming, the plate 105 is pulled between two points, i.e., a base end edge 108a of the die 108 and a tip end edge 109a of the punch 109, and extended as shown in FIG. 12B; therefore, the plate 105 cannot be extended beyond coefficient of extension of its material. Hence, the height of the projection 103 cannot sufficiently be increased with respect to the opening width, and it becomes difficult to increase the gas flow passage in size. By contrast, if the tip end side area of the projection 103 is made relatively narrow, it is possible to increase the height of the projection 103 and to increase the gas flow passage in size, but it becomes difficult to enhance the power collection efficiency. Even for production of not only the above-described fuel-cell separator but also an automobile part, a home electrical appliance part, or the like in which a projection is formed by pressing a plate is to be produced, it is desired that the projection has a sufficient height with respect to the opening width and has a large tip end side area.